The concept of commitment has emerged recently in international business literature especially in explaining importer behaviour as a counterpart of the process of internationalisation. Importer commitment often plays a dominant role as one of the major factors influencing relationships in the exporter-importer dyad and facilitates the process of internationalisation by imparting access to the international market. This critical importer and supplier relationship and its animating factors are, however, overlooked and largely neglected in the literature. Accordingly, it is inconclusive as to which factors influence importer commitment and how they influence it. Drawing on the literature, this study strived to investigate the spectrum of importer commitment and has explicitly examined eight factors influencing importer commitment to a foreign supplier by integrating the factors in a comprehensive model. Cultural similarity between importer and overseas supplier, knowledge and experience of the importer, the supplier's competencies, communication between importer and supplier, the supplier's opportunism, the importer's trust, importer transaction-specific investment, and environmental volatility of the import market have been identified as possible antecedents of importer commitment. Theoretical foundations are drawn basically from transaction cost economics, internationalisation process theory and resource-based theory of the firm to design a basic framework for quantitative investigation. Further, the study endeavors to gain important insights into the phenomena related to the trust and commitment building process through qualitative in-depth interviews. In addition, to validate the qualitative reasoning, a competing quantitative model is developed where trust plays a mediating role for some of the predictor variables in the model. Primary data were collected from a sample of 232 industrial and commercial importers in a developing country for empirical verification of the quantitative models using Structural Equation Modeling. As reported in this thesis, the proposed model with minor modifications fit better with the data compared to the competing model, and it explained 56% of the variance of importer commitment. However, the analysis of the modified proposed structural model revealed that ten out of fourteen hypotheses are significant including five direct paths as antecedents of importer commitment. The mediating role of trust and opportunism in the model is also supported. Twelve interviews were conducted to add in-depth richer insights into the study for further verification of the knowledge development, and trust and commitment building process in the importer-supplier relationship. The findings support most conceptual links in the qualitative model and lend support to most of the hypothesised relationships in the modified competing quantitative model. These findings extend the application of the underpinned theories and their tenets in explaining the importersupplier commitment relationship and contribute to the body of knowledge. Implications of the findings are discussed and future research directions are recommended.